1. Field of Invention
The present invention relates to a method for forming graphite fibers composition and mixtures formed thereby. More particularly, the present invention relates to a method for forming a vapor-grown graphite fibers (VGGF) composition and a mixture containing the VGGF composition formed thereby and applications thereof.
2. Description of Related Art
Recently, with the advance of information, communication, computer and energy industries, electronic products are developed towards the directions of smaller size and higher performance. A conventional skill often adds non-fibrous carbon black to a material such as plastic, rubber etc., thereby promoting thermal conductivity and electrical conductivity of the material. The non-fibrous carbon black is particulate, and thus has to be added in a large amount so as to have some effect on the performance of the material. However, the large amount of carbon black addition has caused the composite material to have inferior physical properties and easy decarburization, thus resulting in contamination problem at a clean room.
Another conventional skill adopts polyacrylonitrile (PAN)-based carbon fibers and pitch-based carbon fibers instead of carbon black. Although these carbon fibers are of continuity, yet their diameters are so large (greater than 10 μm), that the number of networks which can be formed in the composite material is limited, and a large amount of carbon fibers are still needed to have some effect on performance of the composite material, thus still causing the composite material to have the problems of inferior physical properties and easy decarburization.
In order to resolve the aforementioned problems, another conventional skill uses vapor-grown carbon fibers (VGCF) of relatively small diameters to replace the non-fibrous carbon black and the carbon fibers. Since the diameters of the VGCF are quite small (about 50 nm to 200 nm), only a small amount of VGCF is needed to form many continuous networks in the composite material, thus not causing the composite material to have the problems of inferior physical properties and easy decarburization, and maintaining the cleanness of a clean room. In addition, since having the characteristics of excellent thermal and electrical conductivities, and high strength etc., the VGCF have effectively promoted the performance of the composite material. However, the conventional VGCF contains too much non-fibrous carbon which cannot be removed by graphitization, thus decreasing the number of continuous networks to be constructed in the composite material to affect the performance of the composite material. Further, the conventional VGCFs are generally formed in one-dimensional structures which construct much less continuous networks in comparison with three-dimensional VGCFs, and fail to promote strength, thermal and electrical conductivity performances of the composite material as much as expected. Also, since not being highly graphitized, the metal catalyst used in the production of conventional VGCF has not been removed to be within a proper range, which has caused a detrimental effect on electrochemical reaction to be applied in the field of energy, for example, has limited efficacy in promoting the power and cycle life of a battery.
Hence, there is a need to provide an in-situ method to produce a VGGF (vapor-grown graphite fibers) composition with more three-dimensional linkage structures, less non-fibrous carbon, less metal content and a mixture thereof for solving the problems of the conventional VGCF.